In mid-2365, the first officer of the Lantree suffered a case of Thelusian flu. Shortly thereafter, the Lantree stopped at Darwin Station.

The first officer transmitted the disease to the rest of the Lantree crew, who began aging at a rapid rate, and later died. The station personnel also contracted the disease, as did DoctorPulaski later, until a cure was discovered, using the transporter to revert a person's genetic pattern to a previous transporter trace or DNA code. (TNG: "Unnatural Selection")

In the script for ENT: "Shadows of P'Jem" (both the first draft and the final draft), the Thelusian flu is referenced as part of dialogue that was not ultimately included in that installment. Hoshi Sato cited the virus as an excuse for CommanderTucker being absent when VulcancaptainSopek wanted to speak to him, Hoshi claiming that Tucker was in Sickbay because Dr. Phlox believed he had contracted the illness. Remarked Hoshi, "It's very rare and highly contagious."